1. Technical Field
The present invention relates to a control circuit of an image reader, an image reader, a control method of an image reader, and a program.
2. Related Art
In general, an image reader sequentially turns on a plurality of light sources (for example, a red LED, a green LED, and a blue LED) provided in a carriage when reading a monochrome image. In this case, a value of a current supplied to a light source to be turned on may be adjusted by supplying a current to a dummy circuit before supplying the current to the light source.
For example, JP-A-2002-237929 discloses a technique in which LEDs are turned on with the same duty ratio as in reading a color document when reading a monochrome document and currents supplied to the LEDs are made equal by setting the lighting time of each LED to ⅓ at the time of both reading of a monochrome document and reading of a color document. If the technique disclosed in JP-A-2002-237929 is used, a value of a current supplied to each LED provided in a carriage may be adjusted by supplying a current to a dummy circuit as described above.
However, in the case where a light source control circuit is built in an AFE (analog front end) that converts a read image into digital data and outputs the digital data, a noise is added to the digital data output from the AFE by switching of supply of a current to each light source or a dummy circuit.